If you’re betting on Tuesday’s Republican primaries in Michigan and Arizona, the smart play is to short the pundits. For two months, each decree that a candidate possesses momentum has instead been a death knell. Mitt Romney entered South Carolina as the first nonincumbent GOP candidate in a generation to capture the first two contests and got clobbered by a guy who had twice been written off for dead. Newt Gingrich’s lunar lunacy in Florida repositioned Romney as the inevitable nominee, but the coronation was postponed by Rick Santorum’s three-state sweep on Feb. 7, a night everyone said didn’t matter — until it vaulted Santorum to the lead in national polls. For the past two weeks, the Feb. 28 primaries in Michigan and Arizona loomed as a pivotal inflection point, a test of Santorum’s improbable strength and Romney’s improbable weakness. But now that the heavyweight tussle in Michigan has arrived, we’re liable to learn nothing at all.

The high drama on Tuesday is whether Romney can avoid the ignominious distinction of losing his native state, a defeat that would highlight his struggle to court the party’s conservative base. Down by double digits in some polls two weeks ago, Romney and his allied super PAC erased the gap by painting Santorum as a spendthrift Washington insider. By late last week, Romney retook the lead. But both candidates have bumbled since. Santorum spent more time talking about notions of good and evil than about kitchen-table economics. Romney’s economic message has been hampered by his habit of reminding voters in this recession-ravaged state of his vast wealth. While Arizona projects to be a comfortable win for Romney — he leads by an average of 13 points in polls conducted over the past nine days — Michigan may be up for grabs. Romney clings to slight leads in three of the five polls released Monday, while Santorum has an edge in two.

As in earlier states, Romney is pinning his hopes on racking up large margins in the state’s population hub. The former Massachusetts governor grew up in affluent Oakland County, just outside metro Detroit, and the area will be his wheelhouse. Santorum is banking on rural voters and conservative population centers in northern and western Michigan, like Kent County, home to Grand Rapids, and neighboring Ottawa County, a redoubt for religious conservatives that abuts Lake Michigan. Complicating matters is the presence of Ron Paul, who is drawing teeming crowds on the eve of the primary and could corral up to 15% of the vote, partly from crossover voters in a de facto open primary, says Bill Ballenger, the editor of Inside Michigan Politics, a nonpartisan newsletter.

“Romney is going to be hugely wounded if he loses,” Ballenger says. But whether the outcome is a loss may be subject to spin. Tuesday’s contest carries the specter of a split decision, in which one candidate wins the popular vote and another collects a majority of the state’s delegates, which are apportioned according to the winner in each congressional district. “It’s possible somebody could win statewide and lose nine out of 14 congressional districts,” Ballenger predicts.

This muddle is unlikely to produce a dramatic shift in the race; it is poised to drag on indefinitely no matter Tuesday’s results. Romney, Santorum and Gingrich are likely to divvy up the 10 states voting a week from now on Super Tuesday. Polls show Santorum with hefty leads in Ohio, Oklahoma and Tennessee, with Romney headed for a rout in Virginia and Massachusetts and Gingrich poised to scoop up his home state of Georgia — which could presage a resurgence as the contest turns back South.

It’s possible, of course, that Romney notches a pair of comfortable wins and uses them as a springboard to a national surge. But Romney has demonstrated a knack for stepping on his good fortune. The morning after his win in Florida, he coughed up his unfortunate gaffe about the “very poor,” and just as his fortunes brightened in Michigan, he started talking about his fleet of cars and NASCAR-owner friends.

The irony of the Republican race is that a succession of rivals have risen on the argument that they’re not Romney, while Romney is at his best when he points out that he is not them. The former Massachusetts governor is far better at tearing down his antagonists than he is at selling himself, a fact that has raised his own negatives and put some of his supporters on edge. “People want to be uplifted,” Virginia Governor Bob McDonnell, a top Romney surrogate, told reporters Monday. “They want us to be positive, and I’d like to see more of that.” Not being Rick Santorum is no better justification for the Republican nomination than not being Mitt Romney.

Which is why Michigan is less likely to reshape the race than reports have suggested. The only certainty in this turbulent primary season is that nobody knows what will happen next.